1. Field of Invention
This invention relates to material compaction and ejection systems, more particularly, to the ejection door for such systems.
2. Prior Art
With increased demands in the refuse collection industry for trucks having greater mobility and versatility to handle the difficult collection routes having limited access, numerous small compaction units have been developed. Customarily, refuse is collected in the smaller truck at limited access points, compacted, and eventually delivered to a parent truck, where the refuse transfer is accomplished by ejection from the smaller compaction unit.
The door through which the ejected refuse passes (herein referred to as the ejection door) remains closed during the refuse collection/compaction operations and functions as a containing wall for the compacted refuse. This door must, therefore, be capable of withstanding the compaction pressures transferred through the refuse from the compaction blades within the overall system.
In addition to being able to retain the collected refuse and withstand the compaction forces, the ejection door is normally opened in coordinated manner with the operation of the ejection blade within the compaction unit.
Current compaction/ejection systems include both manual and automated ejection door assemblies. A typical manual assembly would simply comprise a latch means which can be released by the operator to allow the ejection door to open for discharge. More common, however, are the automated ejection doors which are hydraulically operated to provide a clear discharge path upon actuation of the discharge blade.
Such automated doors are of single body construction in various geometrical configurations. The nature of geometric design will vary with the type of lift mechanism utilized. For example, a vertical lift door will need to be of such construction so that the hydraulic lifters will not be required to compact refuse caught between the lifting door and the top cover of the compaction unit. It should be noted that a considerable force is being exerted on the door by the compacted refuse, providing a resistance to movement in the vertical direction.
If the vertical ejection door were curved away from the truck body the compacted refuse contained in the curved volume of the door would tend to move with the vertically rising door, developing resistance forces against the nonrising refuse. This results in increased energy and time losses. Therefore, conventional vertical lift doors are flat to minimize this type of resistance during ejection procedures.
To obtain the maximum storage area for refuse, some compaction units use a rearwardly curved ejection door providing additional compaction space beyond the rear portion of the truck bed. To avoid the vertical lift problems previously indicated, a typical ejection door for this configuration would involve hydraulic lifting means which operate to extend the ejection door rearward and upward, thereby avoiding resistive forces which might be exerted by the refuse contained within the curved portion of the door during vertical extension.
Both the straight and curved geometric configurations of the single body ejection door require a substantial full extension of the door body to obtain the full discharge path. This not only requires additional overhead or rearward space at the discharge location, but also requires additional operator time to fully extend the hydraulic cylinders.